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|duration = 8–15 seconds 〔 |map alt = |magnitude = 6.9 Mw 〔 |depth = 〔 |location = 〔 |type = Oblique-slip |countries affected = San Francisco Bay Area United States |damage = $5.6–6 billion 〔 |intensity = IX (''Violent'') 〔 |PGA = .65''g'' (at epicenter) 〔 |tsunami = Yes 〔〔 |landslide = 1,000–4,000 〔〔 |foreshocks = |casualties = 63 killed, 3,757 injured 〔〔 }} The 1989 Loma Prieta earthquake occurred in Northern California on October 17 at local time. The shock was centered in The Forest of Nisene Marks State Park approximately northeast of Santa Cruz on a section of the San Andreas Fault System and was named for the nearby Loma Prieta peak in the Santa Cruz Mountains. With a moment magnitude of 6.9 and a maximum Mercalli intensity of IX (''Violent''), the shock was responsible for 63 deaths and 3,757 injuries. The Loma Prieta segment of the San Andreas Fault System had been relatively inactive since the 1906 San Francisco earthquake (to the degree that it was designated a seismic gap) until two moderate foreshocks occurred in June 1988 and again in August 1989. Damage was heavy in Santa Cruz County and less so to the south in Monterey County, but effects extended well to the north into the San Francisco Bay Area, both on the San Francisco Peninsula and across the bay in Oakland. No surface faulting occurred, though a large number of other ground failures and landslides occurred, especially in the Summit area of the Santa Cruz Mountains. Liquefaction was also a significant issue, especially in the heavily damaged Marina District of San Francisco, but its effects were also seen in the East Bay, and near the shore of Monterey Bay, where a non-destructive tsunami was also observed. Due to the sports coverage of the 1989 World Series, it became the first major earthquake in the United States that was broadcast live on national television. Rush-hour traffic on the Bay Area freeways was lighter than normal due to nearly 62,000 people present at the game at Candlestick Park in San Francisco, and this may have prevented a larger loss of life, as several of the Bay Area's major transportation structures suffered catastrophic failures. The collapse of a section of the double-deck Nimitz Freeway in Oakland was the site of the single largest number of casualties for the event, but the collapse of man-made structures and other related accidents contributed to casualties occurring in San Francisco, Los Altos, and Santa Cruz. ==Preface== The history of earthquake investigations in California has been largely focused on the San Andreas Fault System, due to its strong influence in the state as the boundary between the Pacific Plate and the North American Plate; it is the most studied fault on Earth. Andrew Lawson, a geologist from the University of California, Berkeley, had named the fault after the San Andreas Lake (prior to the occurrence of the 1906 San Francisco earthquake) and later led an investigation into that event. The San Andreas Fault ruptured for a length of during the 1906 shock, both to the north of San Francisco and to the south in the Santa Cruz Mountains region. Several long term forecasts for a large shock along the San Andreas Fault in that area had been made public prior to 1989 (the event and its aftershocks occurred within a recognized seismic gap) but the earthquake that transpired was not what had been anticipated. The 1989 Loma Prieta event originated on an undiscovered oblique-slip reverse fault that is located adjacent to the San Andreas Fault. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1989 Loma Prieta earthquake」の詳細全文を読む スポンサード リンク
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